Just cause it's been done...
...Is never a reason to shy away from an idea. Bleach isn't the only "hero's greatest power can't be controlled" series. Avatar: The Last Airbender, Naruto, The Incredible Hulk, etc, all successful even though the idea had "been done". Fuck Bleach (that has nothing to do with this flash, just fuck Bleach forever). I hope you stick with this, I'd like to see what you accomplish, and like a person with a brain I'd like to judge based on how it actually turns out rather than just whether the idea's been done in some form or not. EVERYTHING has been done in some form.
Two things though. One, this trailer doesn't show a whole lot of frame-by-frame animation, it's mostly tweens and fades. I'm a sucker for fbf, so please include more of that in the first official episode. Also, I believe i can hear your lips separating and smacking together in the audio.... Or... I suppose your tongue losing suction against the roof of your mouth... Like someone chewing food with their mouth open. It's a little offputting.